# age = 14
# if age >= 18:
#     print('yes')
# else:
#     print('NO')
#
#
# username = input('input username: ')
# password = input('input password: ')
# if username == 'admin' and password == '123456':
#     print('YES')
# else:
#     print("NO")

# if 3:
#     print('OK')
#
# if 'hello':
#     print('int -> True')
# else:
#     print('int -> False')
#
# if not None:
#     print('None -> True')

# if ['nus', 'sjkd']:
#     print("list -> True")
# if []:
#     print('list -> False')

# sorce = int(input('input sorce(int): '))
# if 100 >= int(sorce) >= 90:
#     print('youxiu')
# elif 80 <= int(sorce) < 90:
#     print('lianghao')
# elif 70 <= int(sorce) < 80:
#     print('zhongdneg')
# elif 60 <= int(sorce) < 70:
#     print("jige")
# elif int(sorce) < 60:
#     print("not jige")
# else:
#     print('sorce not ')

sorce = int(input("input sorce: "))
if not 0 <= sorce <= 100:
    print("! sorce")
elif sorce >= 90:
    print('A')
elif sorce >= 80:
    print('B')
elif sorce >= 70:
    print('C')
elif sorce >= 60:
    print('D')
else:
    print('E')
